The attitude depends on whether you are looking for a used Yugo or for a new Mercedes. FT-840 is a Yugo. A good companion would be used AL811 or SB220. They are manual switch and manual tune with no safeguards.

VL1000 does autoswitching and autotuning, and possibly an automatic antenna selection.

If the main purpose is strong SSB, the first step is to replace FT-840 with a rig that has RF speech processing. With proper microphone, such a rig at 100W may be as punchy as FT-840 with an amp. 

Ignacy, NO9E

If I remember correctly, the lowest IMD figures from any amp tested in QST were for ACOM2000A, which uses tetrodes. Its linearity may be due to a negative feedback from the cathode resistor.


Could have been true in old times but now probably false, at least with proper biasing and MOSFETs. For instance for KX3, IM3 at 11V supply is about -35db at 3 W level, -32 at 5W and -20 at 10W. See files in KX3 group on yahoo. K3 behaves similarly and also has very slow ALC.

With the new KW transistor (MRFE6VP61K25HR6), IM3 are < 40db at power levels 100 to 600W, and increase to -20db at 1 KW.
See http://www.communication-concepts.com/index.php/amplifiers/2m-1kw/2m-1kw-sspa-freescale-kilowatt-amplifier-2meter-1kw.html

Ignacy, NO9E

RF speech processor in K3 is excellent. Crank it up and K3 barefoot sounds like another radio with a 500W amp. Very easy to use TX and RX equalizers.  Any headset can be plugged in without any connector and can be made to sound like Heil HC5 (or anything else). The receiver sounds noisy but with adjustments to AGC threshold and AGC hold While using RF gain the end effect is very nice. 

It seems bad economics to choose a cheap rig while getting an Alpha amp.

Ignacy, NO9E 

This is doable for 2 of RCS-4 positions (+12 and AC) after adding a diode and a capacitor. But there may be current limitations.
Ignacy, NO9E

My RCS-4 is up for 10 years. Used with TT Centurion. A few problems,  always due to something else.

The design of RCS-4 does not tolerate very high SWR at legal limit.

If my RCS-4 fails and is too hard to fix, I would buy another one in a second. There is nothing close at its price point.

Ignacy, NO9E

1k-fa, 2k-fa, and forthcoming 1.3-fa are much newer options than the Icom.
A
KPA500 with KAT500 are probably even better if 600W is enough.
Ignacy, NO9E

Conditions not great but not bad.

It could be the vertical if it is obstructed. I have a DX77 vertical mounted 5 ft up, and compared to dipoles it gives me signal level 10 db down and the noise level 5 db up.

You can compare the vertical and the dipole on 15m.

Ignacy, NO9E

For mobile operations it is enough to have a power supply deliver only about 30% of max current if supercapacitors are used. See MFJ-4403 or Gamma power supply for ideas.

Same for fixed operations. Perhaps one can put a 2 lb 48v/7A power supply inside ALS-600 + supercapacitors. Will be a 17 lb 600W amp.

Ignacy

The band are very noisy at home. Usually S2 to S7. Most seem like white noise.

The bands were much more quieter at a mountaintop. Amazingly often S0 with weak far-away DX that I seldom hear at home.

Ignacy, NO9E

At home the DX is there but not exceptional with 2 el quad.

At top of the mountain with some vertical wire, zillions of DX.  Due to lack of RFI at home QTH that blankets the weaker sigs.

Ignacy, NO9E

It all depends on the antenna and the range of the internal tuner. In a nutshell, the internal tuner is more convenient. Major differences arise when the antenna is badly unbalanced and shows high common currents. With the external tuner, one can have a balun between the radio and the tuner. Such a balun can be very simple as it works at low SWR. With internal tuner the balun needs to be connected to the antenna and must be able to tolerate high SWR with low losses.  With some loads such a balun can absorb nearly all the power sent to the antenna.

I face this issue in portable situations where the antenna is a vertical wire and 1-2 radials. One setup is IC7000 with Z11Pro tuner. The jumper and the control cable to the tuner are both wrapped 10 times around a toroid. Never any evidence of RF current or heating from 160 to 10. The other setup is K3 with internal tuner and an external balun. Smaller baluns are getting hot on some bands really fast.

Ignacy, NO9E

I have a 160/80/40 W9INN dipole at about 50 ft. Excellent SWR at centers of resonance. However, the bandwidths on 80m and 160m are very narrow.  Also, this dipole is some 5-10db down on 160/80 than an 80m dipole fed by ladderline at 60ft. 

I feel that the efforts to tune a multiband dipole with coils is not worth it. Especially when one has access to automatic antenna tuners. 

Ignacy, NO9E

I have 2 el 6 band band quad at 40 ft and 2el 6m quad at 30ft. Both on top of my house. The noise floor of the quad at 30ft is some 10 db higher due to picking up more noise from the house.

The effect of higher elevation is usually much bigger than the effect of more elements. See
http://www.hamradiodeals.co.uk/forums/viewtopic.php?f=45&t=16602

More less, moving from 1/2 lambda to 1 lambda brings 6db, and from 1 to 2 lambda on far away contacts an extra 6 db. So moving from 30 to 40 feet on 20m could add 2 db and reduce the noise. For comparison, adding an extra element to a yagi usually provides 1 db.

Lots of optimistic reports by guys replacing a  $500 antenna by a $5000 antenna.  Unless the height is changed, the reports most likely have as much value as 20db extra by moving from a KW to 1.5 KW amplifier.

Ignacy, NO9E 

I have P3 and KRX3. KRX3 is useful in for me in two situations:
1. Diversity receive during 160m.
2. Intense pileup.

Under small pileups P3 can identify the DX frequency. Under intense pileups stations call all the time and then KRX3 is useful again.

Ignacy, NO9E